Background

Lactobacillus acidophilus is a member of the Lactobacillus genus of bacteria. These bacteria can be found in the mouth, intestine, and vagina. L. acidophilus is thought to benefit health, since it produces vitamin K and lactase. However, L. acidophilus cannot make many other vitamins and amino acids. Because of this, L. acidophilus is mostly found in the upper gastrointestinal (GI) tract where there are higher amounts of these nutrients.

L. acidophilus is commonly used in food, such as yogurt, other dairy products, and fermented soy products, such as miso and tempeh.

L. acidophilus is one of the most commonly used probiotics, microorganisms that are used to promote health. Probiotics are different from prebiotics, which are complex sugars that may support the growth of "good" bacteria in the intestinal tract. The word "synbiotic" means that a product has both a probiotic and a prebiotic.

There is good evidence for the use of L. acidophilus in treating vaginal infections. However, there is unclear evidence for other medicinal uses of L. acidophilus, such as in irritable bowel syndrome, brain disorders, asthma, high cholesterol, lactose digestion, or diarrhea.

Although it is thought to be safe with few side effects, L. acidophilus by mouth should be avoided in people who have intestinal damage, immune problems, or an overgrowth of bacteria in the intestines. These people may have a higher risk of having the bacteria leave the GI tract and possibly cause multiple organ failure. There have been reports that some Lactobacillus species, such as L. rhamnosus and L. casei, may be involved in infections, such as abscesses, meningitis, and septic arthritis.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older)

According to expert opinion, taking 1 x 109 living L. acidophilus cells by mouth in divided doses daily is an adequate dose for most people. Higher amounts may lead to mild stomach problems, while smaller amounts may not be enough. Most formulations base dosage on the number of living organisms, but dry weight has been used in some cases (e.g., 1.5 grams of L. acidophilus).

L. acidophilus supplements taken with antibiotics may kill L. acidophilus.

To treat type 2 diabetes, capsules containing one gram of Lactobacillus acidophilus NCFM have been taken by mouth daily for four weeks.

To prevent traveler's diarrhea, 1011 colony-forming units (CFU) of Lactobacillus acidophilus has been taken by mouth daily for three weeks.

To treat hepatic encephalopathy (confused thinking due to liver disorders), a freeze-dried L. acidophilus preparation called Enpac® has been taken by mouth daily in doses of 20-90 grams (107 organisms per gram) for up to six weeks.

To treat high cholesterol, a dose of 3 x 1010 L. acidophilus organisms has been taken by mouth three times daily for six weeks. A dose of 200 grams of L. acidophilus yogurt has been taken by mouth daily for four weeks. A dose of 125 milliliters of L. acidophilus fermented milk has been taken by mouth three times daily for three weeks.

To improve immune function, clotted milk (containing 1010 CFU of L. acidophilus per 100 grams of milk product) has been taken by mouth daily for five weeks.

To treat intestinal disorders, such as irritable bowel syndrome (IBS), L. acidophilus has been taken by mouth in a dose of 5 x 109 heat-killed organisms, twice daily for six weeks. A dose of 240 milliliters of L. acidophilus milk (7-9 x 106 CFU per milliliter) has been taken by mouth daily for two weeks. One capsule of L. acidophilus-SDC 2012, 2013 (2 x 109 CFU per milliliter) has been taken by mouth twice daily for four weeks.

To treat lactose intolerance, 1010 CFU of L. acidophilus and L. acidophilus fermented milk has been taken by mouth. Single 400-milliliter doses of milk containing one of four different strains of L. acidophilus (ATCC 4356, B, N1, or E) have been taken by mouth.

To prevent vaginal disorders, a vaccine containing L. acidophilus (Gynatren®) has been injected in three doses of 0.5 milliliters every two weeks (with a booster after 12 months) or every seven days together with standard treatment (tetracycline-amphotericin B suppositories, for insertion into the vagina).

To treat vaginal disorders, including bacterial and yeast infections, eight ounces or 150 milliliters of 108 CFU per milliliter of L. acidophilus yogurt have been taken by mouth daily. One to two tablets or capsules (Gynoflor® or Vivag®) (107-109 CFU per tablet or capsule) have been inserted into the vagina once or twice daily for up to three months. Preparations containing Lactobacillus acidophilus (Calagin®, SIFFRA®) have been inserted into the vagina every other day for 10 days after menstruation for three months. A yogurt douche, made by adding water to 10-15 milliliters of yogurt (108 CFU per milliliter of L. acidophilus), has been inserted into the vagina twice daily for two months.

To treat keratoconjunctivitis sicca, an eye disease, eyedrops containing a diluted Lactobacillus acidophilus saline solution (2 x 108 CFU per milliliter) have been applied to the eyes four times daily for four weeks.

Children (younger than 18 years)

Some experts suggest that 1/4 teaspoon or 1/4 capsule of commercially available supplements, taken by mouth two hours after each dose of antibiotics, may help replace "good" bacteria in the gut. Up to 1012 lyophilized heat-killed L. acidophilus cells have been taken by mouth every 12 hours for up to five days.

L. acidophilus supplements taken with antibiotics may kill L. acidophilus.

To treat allergic skin reactions, L. acidophilus (3 x 109 lyophilized cells) has been taken by mouth daily for the first six months of life. A dose of 150 milliliters of milk fermented with L-92 has been taken by mouth once daily for eight weeks. Milk components supplemented with 900 milligrams of dextrin and 100 milligrams of heat-inactivated L-92 have been taken by mouth once daily for eight weeks.

The World Health Organization (WHO) reports that treating acute diarrhea in children involves drinking plenty of fluids and supplementing with heat-killed L. acidophilus. To treat diarrhea, Lactobacillus acidophilus in doses of 1010 colony-forming units (CFU) has been taken by mouth twice daily for five doses. Heat-killed L. acidophilus (Lacteol®) has been taken by mouth along with rehydration therapy for up to 4.5 days. Lacteol Fort® (109 lyophilized heat-killed L. acidophilus LB cells) has been taken by mouth with five milliliters of water in five doses at 12-hour intervals following rehydration therapy.

To improve immune function, L. acidophilus has been taken by mouth in doses of 3 x 109 lyophilized cells dissolved in 1-2 milliliters of water daily for the first six months of life. Acilact has also been taken by mouth.

To treat the flu, milk mixed with L. acidophilus (1 x 109 CFU) has been taken by mouth in two daily doses for six months.

To prevent necrotizing enterocolitis, a disease involving the death of intestinal tissue, L. acidophilus has been taken by mouth with formula by premature infants beginning at three weeks of life. A solution containing one gram (6 x 109 CFU) of living or killed L. acidophilus bacteria has been delivered to the stomach of newborns via a feeding tube.

To treat thrush of the mouth, 1/4 teaspoon or 1/4 capsule of L. acidophilus in water has been taken by mouth.

To treat diaper rash or yeast infection, liquid preparations of L. acidophilus have been applied directly to the skin in the diaper area.

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Vaginal disorders

There is good evidence supporting the use of L. acidophilus or yogurt enriched with L. acidophilus for the treatment of vaginal infections. More evidence is needed to support the use of L. acidophilus in treating vaginal yeast infections such as candidiasis, as well as restoring microorganisms in the vagina after treatment for infections. Several studies have used L. acidophilus in combination with other probiotics or supplements, such as vitamin B.

C

Allergic skin reactions

Taking Lactobacillus by mouth along with itraconazole has been shown to help treat scaly, itchy rashes. There is also some evidence that Lactobacilli may help prevent this condition. However, other studies did not produce the same results. Some found that L. acidophilus supplementation may increase the risk of sensitivity to food allergens, while others suggest that L. acidophilus may actually decrease sensitivity. More research is needed in this area.

C

Anemia

Limited research shows that L. acidophilus combined with iron amino acid chelates may improve measures of anemia, including red blood cell counts and levels of hemoglobin. However, it may lack benefits on other measures, such as cell volume, cell hemoglobin, and serum iron levels. Further research is needed before conclusions can be made.

C

Ankylosing spondylitis

Limited research suggests that a probiotic combination containing L. acidophilus may help reduce symptoms of ankylosing spondylitis, arthritis of the spine. However, further research is needed to confirm this and to determine the effects of using L. acidophilus alone.

C

Asthma

Limited research found unclear and negative evidence to support the use of L. acidophilus in treating allergic asthma. More research is needed in this area.

C

Cavities

Limited research shows that eating probiotic ice cream containing L. acidophilus may reduce levels of microorganisms in the saliva that may be linked to cavities. Further research is needed to confirm this and to identify the effects of L. acidophilus alone.

C

Diabetes (type 2)

Limited research suggests that taking capsules containing L. acidophilus may lower insulin sensitivity in people who have type 2 diabetes. Further research is needed.

C

Diarrhea prevention

It is unclear whether L. acidophilus, or probiotics in general, may prevent diarrhea. One study found that L. acidophilus alone lacked benefits in preventing traveler's diarrhea, while others found conflicting results when using combination probiotic strains (such as Lactinex™, a blend of L. acidophilus and L. bulgaricus). There is also conflicting evidence on whether probiotic treatments containing L. acidophilus help prevent antibiotic-associated diarrhea in babies and adults, as well as whether probiotics prevent diarrhea more effectively in children.

C

Diarrhea treatment (children)

The World Health Organization (WHO) reports that treating acute diarrhea in children involves drinking plenty of fluids and supplementing with heat-killed L. acidophilus. However, studies have found conflicting results, and it is still unclear whether L. acidophilus shortens the duration of diarrhea. One study reported that a combination of heat-killed L. acidophilus and zinc therapy had negative results, compared to zinc alone. It is also unclear whether live Lactobacilli, alone or in combination with other treatments, are effective in treating diarrhea. An early study found that live probiotic blends containing L. acidophilus were ineffective, while others reported probiotic treatments to be effective.

C

Eye diseases

Low-quality studies found that eyedrops that contain L. acidophilus may help reduce symptoms of an eye disease called keratoconjunctivitis sicca. Further research is needed before conclusions can be made.

C

Flu

Limited research suggests that L. acidophilus may reduce fever and the duration of flu symptoms. However, further research is needed before conclusions can be made.

C

Hay fever

Animal research suggests that L. acidophilus may reduce allergic immune responses. There is some evidence that milk containing L. acidophilus may relieve hay fever symptoms, but other studies found conflicting results. More research is needed to understand how L. acidophilus may relieve allergies.

C

Helicobacter pylori infection

Some strains of probiotic bacteria may block the growth H. pylori and treat or prevent H. pylori infection. However, studies suggest that L. acidophilus lacks this effect on H. pylori. Yogurt containing L. acidophilus and B. lactis was reported to decrease H. pylori activity and improve antibiotic therapy in H. pylori infections, but this effect was likely due to B. lactis. Other Lactobacillus species may be more effective, such as L. paracasei, L. rhamnosus, L. plantarum, L. casei, and L. johnsonii.

C

Hepatic encephalopathy

One study found that probiotics containing L. acidophilus may reduce toxins in the blood, which may help prevent hepatic encephalopathy (confused thinking due to liver disorders). However, other studies found unclear or negative evidence. Further research is needed in this area.

C

Immune function

Probiotics may help enhance the immune system at an early age and prevent allergic disorders later in life. Combination probiotic supplements have been shown to affect the adult immune system. Early studies found that L. acidophilus supplementation may affect early immune responses to allergens and vaccines. However, there is conflicting evidence. Effects on other immune disorders remain unclear.

C

Intestinal disorders

Studies report that combination probiotic preparations containing L. acidophilus may help treat intestinal disorders such as irritable bowel syndrome (IBS). L. acidophilus may also help standard therapies for partial bowel blockages. However, combination probiotic preparations with L. acidophilus lack benefits in critically ill people with gut disorders. There is unclear and conflicting evidence supporting the use of L. acidophilus alone in treating IBS.

C

Lactose intolerance

Lactic acid bacteria are thought to promote lactose digestion by breaking down lactose or releasing compounds that help digest it. However, there is unclear and conflicting evidence to support the use of L. acidophilus for this purpose.

C

Liver disease

Limited research using a combination treatment has shown that probiotic treatment may improve the symptoms of liver disease in certain patients, but further studies are still needed before conclusions may be made. In addition, studies assessing the effects of L. acidophilus alone are still needed.

C

Necrotizing enterocolitis (NEC) prevention

Limited research suggests that treating newborns with solutions containing living or killed L. acidophilus bacteria may help reduce necrotizing enterocolitis, a disorder involving the death of intestinal tissue. Further research is needed before conclusions can be made.

C

Pneumonia

Limited research shows that pneumonia has been treated with a combination of antibiotics and L. acidophilus. However, further details are unclear.

C

Pouchitis

Limited research suggests that a combination therapy involving L. acidophilus may prevent relapse of pouchitis, inflammation of the ileal pouch after surgery. Further research is needed to confirm these results and to identify the effects of L. acidophilus alone.

C

Pregnancy problems

Vaginal disease caused by bacteria may lead to preterm delivery and low birthweight. There is some evidence that L. acidophilus may help prevent preterm delivery, though more evidence is needed.

C

Radiation-induced diarrhea

Limited research shows that diarrhea caused by radiation may be reduced with combination therapy involving L. acidophilus. However, further research is needed to confirm these results and to identify the effects of L. acidophilus alone.

C

Sepsis

Limited research shows that treating newborns with solutions containing living or killed L. acidophilus bacteria may help prevent sepsis, a severe response to bacteria or germs. More studies are needed before conclusions can be made.

D

High cholesterol

There is conflicting evidence as to whether combination probiotics containing L. acidophilus may benefit high cholesterol. Although L. acidophilus has been shown in some studies to lower cholesterol, this effect may be due to bile acids.

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Interactions

Interactions with Drugs

Lactobacillus may affect insulin sensitivity. Caution is advised when using medications that may also affect insulin sensitivity or blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

Lactobacillus may also interact with agents that may affect the immune system, agents that may treat arthritis, agents that may treat asthma, agents that may treat diarrhea, agents that may treat heart problems, agents that may treat stomach problems, agents that may treat ulcers (such as rabeprazole), alcohol, antibiotics (such as amoxicillin, bacampicillin, clarithromycin, enoxacin, and furazolidone), antivirals, benzodiazepines, birth control, cholesterol-lowering agents, esomeprazole, iron salts, tinidazole, and vaccinations.

Interactions with Herbs and Dietary Supplements

Lactobacillus may affect insulin sensitivity. Caution is advised when using herbs or supplements that may also affect insulin sensitivity or blood sugar. Blood sugar levels may require monitoring, and doses may need adjustment.

Lactobacillus may also interact with antibacterials, antivirals, birth control, calcium, cholesterol-lowering herbs and supplements, herbs and supplements that may affect the immune system, herbs and supplements that may treat arthritis, herbs and supplements that may treat asthma, herbs and supplements that may treat diarrhea, herbs and supplements that may treat heart problems, herbs and supplements that may treat stomach problems, herbs and supplements that may treat ulcers, iron, phytic acid, prebiotics, and probiotics.

Methodology

This information is based on a systematic review of scientific literature and was peer-reviewed and edited by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Note: This bottom line does not provide an in-depth analysis of L. acidophilus used in combination therapies. When available, studies using L. acidophilus alone are discussed in detail.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

People who are sensitive to lactose may develop stomach discomfort or other side effects from products that contain L. acidophilus. This is not caused by the bacteria, but by the trace amounts of lactose that they may contain from the manufacturing process.

L. acidophilus supplementation in the first six months of life may increase the risks for allergies to cow's milk in some children.

Studies show that taking up to 1011 live L. acidophilus cells by mouth, twice daily for up to eight weeks, may lack effects on immune changes caused by allergies.

Avoid if allergic or sensitive to Lactobacillus acidophilus, its parts, or members of the Lactobacillaceae family.

Avoid in people who have milk allergies, due to possible milk allergens in L. acidophilus preparations made from dairy products.

Side Effects and Warnings

L. acidophilus is likely safe when used appropriately in the general population of children and adults. L. acidophilus has been well tolerated, with few side effects reported. The most common side effect is gas, which usually decreases with continued use. Though some Lactobacillus strains have been linked to infection, the probiotic use of these strains is generally considered safe. Some research suggests that half of the reported serious cases of infections due to Lactobacillus tend to occur in people with immune problems.

Use cautiously in people who have stomach disorders. High doses (over 109 cells daily) have been linked to mild stomach problems.

Use cautiously in people who have short bowel syndrome. Lactobacillus may cause bacteremia, a condition in which there are bacteria in the blood.

Use cautiously in people who have a high fever.

Use cautiously in people who have fixed orthodontic appliances (i.e., braces), chewing problems, or misaligned teeth, as L. acidophilus may cause tooth decay.

Use cautiously in infants and children. L. acidophilus supplementation in the first six months of life may increase the risks for allergies to cow's milk in some children. Although L. acidophilus has been shown to reduce colic in infants, there is not enough evidence about the safety of long-term L. acidophilus use in this age group. Bacteremia and sepsis, or shock, have been reported after pediatric use of probiotics. There is a report of severe dehydration in a child with diarrhea after treatment with rehydrating solution and Lacteol® by mouth.

Avoid if allergic or sensitive to Lactobacillus acidophilus, its parts, or members of the Lactobacillaceae family.

Avoid in people who have milk allergies, due to possible milk allergens in L. acidophilus preparations made from dairy products.

Avoid in people who have immune problems, as Lactobacillus may cause disease.

Pregnancy and Breastfeeding

Lactobacillus has been used safely during pregnancy (2-4 weeks before childbirth) and breastfeeding (for up to six months).

L. acidophilus vaginal tablets have been studied in pregnant women for the treatment of bacterial vaginosis. An L. acidophilus-containing culture (Narine) has been studied in pregnant women for treatment of suppurative inflammatory disease, with side effects lacking. Studies have found that higher Lactobacilli levels in the vagina may be linked to a lower risk of premature childbirth, and L. acidophilus has been studied in pregnant women to prevent premature childbirth.

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